The effect of laser pulse shape variations on the adiabat of NIF capsule implosions

Journal Article · Wed May 15 00:00:00 EDT 2013 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4807331· OSTI ID:22218622

Robey, H. F.; MacGowan, B. J.; Landen, O. L.; LaFortune, K. N.; Widmayer, C.; Celliers, P. M.; Moody, J. D.; Ross, J. S.; Ralph, J.; LePape, S.; Berzak Hopkins, L. F.; Spears, B. K.; Haan, S. W.; Clark, D.; Lindl, J. D.; Edwards, M. J. ^[1]

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1. LLNL, Livermore, California 94550 (United States)

Indirectly driven capsule implosions on the National Ignition Facility (NIF) [Moses et al., Phys. Plasmas 16, 041006 (2009)] are being performed with the goal of compressing a layer of cryogenic deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) to sustain the self-propagating burn wave that is required for fusion power gain greater than unity. These implosions are driven with a temporally shaped laser pulse that is carefully tailored to keep the DT fuel on a low adiabat (ratio of fuel pressure to the Fermi degenerate pressure). In this report, the impact of variations in the laser pulse shape (both intentionally and unintentionally imposed) on the in-flight implosion adiabat is examined by comparing the measured shot-to-shot variations in ρR from a large ensemble of DT-layered ignition target implosions on NIF spanning a two-year period. A strong sensitivity to variations in the early-time, low-power foot of the laser pulse is observed. It is shown that very small deviations (∼0.1% of the total pulse energy) in the first 2 ns of the laser pulse can decrease the measured ρR by 50%.

• OSTI ID: 22218622
• Journal Information: Physics of Plasmas, Vol. 20, Issue 5; Other Information: (c) 2013 © 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
36 MATERIALS SCIENCE
CAPSULES
COMPARATIVE EVALUATIONS
DEUTERIUM
D-T OPERATION
LASER IMPLOSIONS
LASER TARGETS
LASER-PRODUCED PLASMA
PULSE SHAPERS
PULSES
SILICON OXIDES
THERMONUCLEAR IGNITION
THERMONUCLEAR REACTORS
TRITIUM
US NATIONAL IGNITION FACILITY
VARIATIONS